It is well known to input alphanumeric data using a single stroke keyboard, for example, to a personal computer. A "QWERTY" keyboard is a well known keyboard wherein each key represents a particular character, the first six being labelled QWERTY from left to right. Disadvantages of such an input device include the amount of space required for the keyboard and the non-intuitive arrangement of the keys therein. The required space for a keyboard is typically limited by the number of keys necessary for the characters to be made available and the key space necessary to maintain reliable data input, i.e. to avoid multiple keys being depressed.
It is possible, however, to reduce the size of an input device, i.e. a keyboard, without reducing the number of characters which can be selected. This can be accomplished either by (i) reducing the size of the keys themselves or (ii) decreasing the number of keys and increasing the number of keystrokes. Reducing the size of the keys, however, is not a practical solution due to the aforementioned problem of multiple key depression. A "QWERTY" keyboard employed in a wireless handset, for example, would require the user to exhibit considerable accuracy in selecting the desired character. Therefore, in order to meet both requirements, one must use an input device that requires multiple keystrokes.
Prior art devices take advantage of the fact that the same number of characters on a single stroke keyboard can be made available on a keyboard with fewer keys by incorporating multiple keystrokes.
As an example of such a prior art device, the reader is directed to U.S. Pat. No. 5,003,503, issued Mar. 26, 1991, naming Lapeyre as inventor, the disclosure of which is hereby incorporated by reference. The Lapeyre patent provides for a 7 and 12 key input device that works on the general premise that a first key stroke identifies a group of characters from which a character is selected by a second key stroke. The drawbacks of such an arrangement are twofold.
First, the location of a character within its respective group of characters does not determine the second keystroke key which must be pressed to select the character. This arrangement, similar to the "QWERTY" keyboard, results in a non-intuitive method of data input in which the user must search for the appropriate selection key. Such a device therefore requires extensive use in order for a user to become familiar with its input arrangement, thus making the device cumbersome for a first time or periodic user.
Second, as a result of all available characters and their corresponding secondary keystroke number being labelled on the keys, the Lapeyre device is very cluttered and difficult to read. Again, this increases the input difficulty for a first time or periodic user.
There exists, therefore, a need for providing a clear and intuitive method of data input in an area of limited space.